1. Field of the Invention
The present invention relates to a robot off-line simulation apparatus for performing simulation of operation of a robot, more specifically a robot off-line simulation apparatus having a function of obtaining an optimum placement for a robot.
2. Description of Related Art
A robot off-line simulation apparatus for performing off-line simulation of operation of a robot is known to the public. When simulation of operation of a robot is performed with this apparatus, generally the three-dimensional models of a robot, a workpiece, a peripheral device, etc. are placed and displayed -on a screen simultaneously. Obviously, the result of the simulation varies to a large degree depending on where the robot is placed on the screen (more precisely, in a space represented by the robot off-line simulation apparatus). If the robot is placed at an inappropriate position, it causes problems such that a task point or a part of an operation path for the robot proves to be in a region where the robot cannot operate, or that the robot interferes with a peripheral device when the robot is made to operate on an intended sequence of task points or an intended operation path.
Hence, conventionally, an operator obtains a robot placing position that satisfies the conditions that the robot should be able to operate at all the task points or over the entire operation path, and that the robot should not interfere with the peripheral device, through a trial-and-error process of placing the robot on the screen over and over. However, even when a robot system is built on the basis of a robot placing position determined to satisfy the conditions as mentioned above, it is not rare that problems occur such that the determined placing position is not optimal, so that the cycle time and duty of the robot exceed stipulated values. Problems like these are dealt with by reviewing and changing the placing positions for the robot, the workpiece and the peripheral device.
Further, even when a robot placing position thought to produce good results is determined in the simulation system in the conventional manner described above, problems occur such that when the real robot is placed at the determined placing position on an actual working site, it turns out that the robot cannot operate at the determined placing position on the actual working site although on the screen, it appears to be able to operate. Hence, the robot placement needs to be changed on the working site, which is very inefficient. This comes from the fact that it is actually very difficult to make the on-screen positional relationship between the robot and the peripheral device perfectly correspond to the real positional relationship between them. Generally, it is inevitable that the former differs from the latter to some degree. It is to be noted that Japanese Unexamined Patent Publication No. 2001-166806 refers to the related art.
As mentioned above, there are following problems: Even if a robot placing position thought to ensure that the robot will be able to operate at all the task points or over the entire operation path and that the robot will not interfere with the peripheral device is obtained on the robot off-line programming system, it is not sufficient. How it will be on the actual working site needs to be considered. Even if the robot can be placed at a certain position on the screen, it does not mean that the robot can be placed at that position on the actual working site, because there is discrepancy between a placement on the screen and a placement on the actual working site, so that the operating range of the robot on the screen is different from that on the actual working site. Further, the robot placement needs to be reviewed and changed when it causes trouble in the robot operation. As a result, unexpected time and cost is required to build the robot system.
Conventionally, there is no way to check whether the off-line determined robot placing position is optimal or not. Hence, it is after the system is actually built that it turns out that the cycle time and the duty of the robot exceed the stipulated values. Thus, the placing positions for the robot, the workpiece and the peripheral device often need to be reviewed and changed, and hence, unexpected time and cost is required to build the robot system.
Further, with the technique disclosed in the above-mentioned publication, the problems due to the discrepancy between a placement on the screen and a placement on the actual working site cannot be solved, so that there is a high possibility that the placement needs to be changed on the actual working site.